Detection of the presence of solid particles such as sand and a determination of the quantity of produced sand in well bore pipes and other flow systems is important for maximizing oil/gas production rates by avoiding severe damage caused by the sand. Sand may clog well lines, thereby adversely affecting production, and can also contaminate separator tanks. Once sand enters a well pipeline, severe corrosion and/or erosion are likely requiring expensive removal of deep sea and down hole pipelines. Sand production may begin with relatively small quantities, which may then rapidly increase.
There are several currently available techniques for detecting the presence of particulates in a fluid flow-stream. One technique continuously senses the vibration produced by sand impacting a pipe or conduit in which a fluid containing sand flows. Such devices, for example the ClampOn™ meter, are affixed to the pipe, typically at an elbow or at a section of the pipe where the flow has to make an abrupt turn, and use passive ultrasonic listening to detect the vibrations when the sand impacts the pipe. Obvious limitations of such passive listening techniques are that they cannot be used for the straight portions of the pipe or only slightly bending pipes. Passive listening techniques are also affected by ambient noise, which can only be partially compensated for. Other techniques include inserting probes into the fluid flow line that convert the sand impact on the probe to electrical signals.